Development of new localized drug delivery system based on ceftriaxone-sulbactam composite drug impregnated porous hydroxyapatite: a systematic approach for in vitro and in vivo animal trial

Abstract

Purpose: Present investigation deals with an extensive approach incorporating in vitro and in vivo experimentation to treat chronic osteomyelitis, using hydroxyapatite porous scaffolds.

Materials and methods: Hydroxyapatite was synthesized in the laboratory by wet chemical method, different porous scaffolds have been fabricated. In vitro studies include variation of porosity with interconnectivity, pore-drug interfacial studies by SEM-EDAX and drug elution studies (by HPLC) both in contact with PBS and SBF at approximately 37 degrees C. In vivo trials were based on experimental osteomyelitis in rabbit model induced in tibia by Staphylococcus aureus. Characterizations included observation of histopathology, radiology and estimation of drug in both bone and serum for 42 days by HPLC method and subsequent bone-biomaterial interface by SEM.

Results: It was established that lower pore percentage with a distribution of mainly micro-pores were found to be superior over the higher pore percentage both in vitro and in vivo. The criteria was matched with the 50N50H samples which had 50-55% porosity with an average pore size approximately 110 microm, having higher interconnectivity (10-100 microm), moderately high adsorption efficiency (approximately 50%) when loaded with CFS (drug combinations consisting of irreversible b-lactamase inhibitor and b-lactam antibiotic). CFS release from HAp implants were faster in PBS than SBF. Further, both the results of in vitro and in vivo drug elution after 42 days showed release higher than minimum inhibitory concentration of CFS against Staphylococcus aureus. In vivo studies also proved the superiority of CFS loaded HAp implants than parenteral group based on eradication of infection and new bone formation.

Conclusions: HAp based porous scaffold loaded with CFS and designed porosity (in terms of micro- and macro-porosity, interconnectivity) was found to be an ideal delivery system which could locally, sustainably release the composite antibiotic in reliable manner both in terms of in vitro drug elution behaviour in contact with SBF and in vivo animal trial.